/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.log4j;

import org.apache.log4j.spi.OptionHandler;
import org.apache.log4j.spi.LoggingEvent;

/**
 * Extend this abstract class to create your own log layout format.
 * 
 * @author Ceki G&uuml;lc&uuml;
 */

public abstract class Layout implements OptionHandler {

	// Note that the line.separator property can be looked up even by
	// applets.
	public final static String LINE_SEP = System.getProperty("line.separator");
	public final static int LINE_SEP_LEN = LINE_SEP.length();

	/**
	 * Implement this method to create your own layout format.
	 */
	abstract public String format(LoggingEvent event);

	/**
	 * Returns the content type output by this layout. The base class returns
	 * "text/plain".
	 */
	public String getContentType() {
		return "text/plain";
	}

	/**
	 * Returns the header for the layout format. The base class returns
	 * <code>null</code>.
	 */
	public String getHeader() {
		return null;
	}

	/**
	 * Returns the footer for the layout format. The base class returns
	 * <code>null</code>.
	 */
	public String getFooter() {
		return null;
	}

	/**
	 * If the layout handles the throwable object contained within
	 * {@link LoggingEvent}, then the layout should return <code>false</code>.
	 * Otherwise, if the layout ignores throwable object, then the layout should
	 * return <code>true</code>. If ignoresThrowable is true, the appender is
	 * responsible for rendering the throwable.
	 * 
	 * <p>
	 * The {@link SimpleLayout}, {@link TTCCLayout}, {@link PatternLayout} all
	 * return <code>true</code>. The {@link org.apache.log4j.xml.XMLLayout}
	 * returns <code>false</code>.
	 * 
	 * @since 0.8.4
	 */
	abstract public boolean ignoresThrowable();

}
